The mission of the What Works Clearinghouse (WWC), part of the U.S. Department of Education’s (ED) Institute of Education Sciences (IES), is to be a central and trusted source of scientific evidence for what works in education. By reviewing and synthesizing scientific evidence, the WWC is fulfilling part of IES’s overall mission to “provide rigorous and relevant evidence on which to ground education practice and policy.” The objective and transparent procedures and standards used by the WWC to conduct reviews are described in this Handbook.
The basic purpose of evaluation research in education is to test whether interventions help the students they are designed to serve and whether new ideas for interventions still under development are worthy of extension to a wider selection of schools and settings. For the WWC, the term intervention refers to a specific program, product, practice, or policy that is thought to have an impact on a given set of educational outcomes.
However, there are a number of ways to conduct this research, and we want to focus on those that make us the most confident that the effect we see is due solely to the intervention alone, and not to the many other factors that are at play in schools and in the lives of students, such as teachers, school, and family. This type of research provides causal evidence about the effectiveness of interventions and provides the basis for WWC reports.
The Handbook describes the WWC systematic review process and procedures that the WWC uses to locate, screen, and review studies, including assessing the quality of the evidence. Systematic reviews use explicit methods to identify, select, and critically appraise relevant research, and extract and analyze data from studies. A WWC systematic review consists of five steps: 1) developing a review protocol; 2) searching the literature; 3) reviewing studies, which includes screening studies for eligibility, reviewing the methodological quality of each study, and reporting on high quality studies and their findings; 4) combining findings within and across studies; and, 5) summarizing the review.
